1. Field of the Invention
The present invention relates to an on-line hydroenhancement evaluation technique and, more particularly, to a technique for measuring the permeability of a woven fabric (i.e., textile) being subjected to a hydroenhancement process.
2. Description of the Prior Art
In conventional hydroentangling processes, webs of nonwoven fibers are treated with high pressure fluids while supported on an "entangling" substrate wire. Typically, the substrate wire is provided on a drum or continuous planar conveyor which traverses a series of pressurized fluid jets to entangle the web into cohesive ordered fiber groups and configurations corresponding to open areas in the screen. Entanglement is effected by action of the fluid jets which cause fibers in the web to migrate to open areas in the screen, tangle and intertwine.
Hydroenhancement is a term used to describe the hydroentanglement process when used specifically on a woven fabric. In hydroenhancement, the properties of a woven fabric are modified (or "enhanced") by exposing the fabric to a sequence of high pressure water jets to act on the woven, spun thread fibers that make up the fabric. During the enhancement process, fibers from the same or adjacent threads become entangled, decreasing the open spaces among the weft and warp threads.
The above-described loss of openness in the woven fabric during the hydroenhancement process results in a reduction of permeability of the fabric, where permeability is defined as the air that will flow through a unit area of a fabric at a known, controlled pressure drop. The capability of measuring the permeability of a fabric during the hydroenhancement process ("wet" permeability) would be a useful control tool in order to provide an indication of the degree of enhancement for a given fabric, allowing the process to be altered to increase or decrease the degree of hydroenhancement, as required. The capability of measuring the permeability of a fabric at the end of the drying process ("dry" permeability) would be useful as a means of auditing the quality of the finished product, in terms of both the product itself and the efficiency of the machinery used to produced the fabric.